Background: This study tested for differences in personal, social, and environmental correlates of moderate to vigorous physical activity (MVPA) across ethnicity/race in male and female adolescents. Methods: Self-reported MVPA and 47 potential correlates of MVPA were measured in an ethnically/racially diverse cross-sectional sample of adolescents, in Minnesota, who participated in EAT-2010 (Eating and Activity in Teens). Interactions of potential correlates with ethnicity/race on MVPA were tested in linear hierarchical regression models in boys and girls. Results: Boys reported 1.7 more weekly hours of MVPA than girls. White adolescents reported 1.1 to 2.1 more weekly hours of MVPA than nonwhite adolescents. Among girls, neighborhood road connectivity was negatively correlated with MVPA among Hispanic and Asian participants. Among boys, sports participation was positively correlated with MVPA among all ethnicities/races, except Asians. Home media equipment was positively correlated with MVPA among Hispanic boys, but negatively correlated among white boys. Conclusions: A few correlates of physical activity among adolescents differed intersectionally by ethnicity/race and sex. Sports participation and home media equipment may have differing impacts on physical activity across ethnicities and races in boys, whereas neighborhood features like road connectivity may have differing impacts on physical activity across ethnicities and races in girls.